6 minute miles

I had a nice dual workout yesterday morning before work. I was at the gym and swam the advance Ironteam swim set which consisted of 400 X 4
My fastest 400 was 8 minutes during my third set, so I think I'm slowly improving. I coasted through the fourth set, as I was preparing for part 2 of my workout: the run.
I toweled off my tri suit, put on my running shoes, put away the goggles and swim cap, grabbed a new electrolyte drink bottle and headed over to the treadmill.
After a 20 minute warmup, to get adjusted to the upright position again after my swim session, I started the speed portion of the workout. This consisted of three 8 minute speed segments with a 3 minute jog in between.
I started with 9 min miles...8 min miles...7.5 min miles....7..... and finally to 6 min miles!
Wow, I don't remember running 6 min miles even when I was 20 years younger.
Not bad for an old fart.
Maybe there is something to this Ironman training.